Elevator systems include a machine for moving the elevator car vertically through a hoistway. Different types of machine arrangements are useful for different building configurations. Taller buildings and high rise buildings often include a traction-based machine arrangement and a roping assembly for suspending the elevator car and a counterweight. The machine causes movement of the roping assembly to cause desired movement of the elevator car.
The roping assembly in a traction based elevator system follows a designed pathway based upon the location of sheaves within the hoistway. In taller buildings, the length of the roping assembly combined with the ability of a building to move in response to high wind, thermal or earthquake conditions introduces the possibility for undesired movement of the roping assembly out of the designed path. A variety of sway mitigation devices have been proposed to address situations, such as an earthquake, when there is lateral movement of the roping assembly. Many such devices are designed to be retracted out of the pathway of the elevator car and selectively moved into a position to contact the roping assembly to reduce roping sway. Another type of sway mitigation approach utilizes “car followers” which are roped carriages that are 2:1 roped devices that are pulled up and reside under the car to limit compensation rope motions. These add weight to the machine and ropes which are undesirable limitations.
Ultra-high rise buildings introduce further complexities because there may be static deflection or drift of the building, which includes a steady-state deflection, in addition to building sway, which includes motion such as oscillation. Some previously proposed sway mitigation devices may not be useful for such drift conditions because the device has to move into the pathway of the elevator car to be effective. Additionally, the condition of the roping assembly may be such that the sway mitigation device is unable to have an effect on the position of the roping assembly based on the manner in which the sway mitigation device is situated within the hoistway.
It is necessary to provide protection for an elevator roping assembly in buildings, such as ultra-high rise buildings, where there may be static building drift that introduces the potential for damage to the roping assembly or interference with normal elevator system operation.